MPLS MTU PROBLEM

Hi,

We have problem with mtu when mpls is active
Clients canot open all sites , eoip vpns dont works .
This happens only when mpls is active on wireless between two routers.
between cisco router and cisco 3550 is fiber .
On cisco 3550 is set mtu 1546 on fastethernet
between R1 and R2 is wirless link , CM9 or XR5 card , L2mtu is 2290 , ip mtu 1500 , mpls mtu 1546
R1 ethernet L2mtu is 1526 , and mpls mtu is 1526 , ip mtu is 1500
R2 L2 mtu on wireless 2290 , mpls mtu 1546 , ip mtu 1500
C1 is cleinet router with simple ip connectivity , public ip address, without mpls.
Problem is when i turn on mpls on R2 clients have problem , when turn off mpls all problems gone.
Mpls is always active on R1.
It looks like mtu problems on wireless , like mpls mtu dont works on wireless or l2mtu is not 2290.
Router OS is v4.10

cisco router ------ cisco 3550 ----- R1 ------- R2 ------- C1

You have to set up mpls mtu the same on all routers. In your setup max possible mpls-mtu is 1526.

Why i have to set up same? Plz explain. i also see that you support vpls fragmentation is that because you have hardware with max 1522 / 1526 mtu?
I have mpls running on cisco routers all different mpls mtu , like 1600 or 1546 and all running excellent.
as i know that value is just max payload mtu with mpls/vpls tags , router dont use max all the time.
Also on mikrotik router with only ethernet running mpls mtu is set to diffrent values 1526 and 1546 and vpls tunnel is working.

Thank you

Problem not Solved.
does anyone have mpls running on mikrotik routers with cisco routers and that is working all ok?

Could you share the solution to your problem with us ?

Hi , There is still problem on wireless linke when mpls is active .

all rb 600 that i have and that is connected to 3550 and so on fiber , cisco routers working fine
but all routers connected with wireless link to core after configuring mpls working wery bad.

Things that happening .

  • after configuring mpls all working ok but after 1 h , clients connected to wireless mikrotik routers dont have access to internet
  • on some routers after configuring mpls , right away stop working access to internet
  • so mpls and internet for client working only if router is connected to fiber .

client config

-public ip
-nat for private network

  • maybe some dst nat

  • maybe some piblic ip on lan for www , mysql server etc..

  • infrastructure routers

-Mikrotik RB 600 , RB 800

  • all puclic ip
  • wireless card are in bridge ( 3 or 4 ) on mikrotik router
  • loopback interface for ospf
  • few ospf areas
    -mpls mtu set to 1526 an all routers
    i ping some locations on my network , ping without mpls is 1472 without fragmentation , and some 15 minutes after activating mpls ping is just 1468 mtu max without fragmentation.

anyone alse have problems?

is there anyone that is using cisco and mikrotik running well mpls for vpn services and access to internet for clients???

here the config from cisco
hw mtu on cisco is 1600

interface GigabitEthernet0/0/0.300
description xxxxx
encapsulation dot1Q 300
ip address x.x.x.x
ip mtu 1500
ip ospf priority 10
mpls label protocol ldp
mpls ip
cdp enable
end

or

interface GigabitEthernet0/0/0.300
description xxxxx
encapsulation dot1Q 300
ip address x.x.x.x
ip mtu 1500
ip ospf priority 10
mpls mtu 1526
mpls label protocol ldp
mpls ip
cdp enable
end

sh mpls forwarding-table detail

100 5566 x.x.x.x/30
763323 Gi0/0/0.300 x.x.x.x
MAC/Encaps=18/22, MRU=1526, Label Stack{5566}
000C423C91D80024975C02008100014A8847 015BE000
No output feature configured



to add , i need ip mtu 1500 command coz ospf is running
no matter what value is mpls mtu , network is acting same ( canot open https sites and so on )



Can you confirm that is problem with ip mtu / mpls mtu ?

I had this problem too, I think its a bug in MT, but the only way I could get MPLS to work reliably was to specify the specific MTU on each interface under MPLS->MTU setting, using the “all” never worked, and people started losing internet about an hour afterwards. So all interfaces on all routers were specifically set to 1508, no more “all” anymore.